Operational amplifiers (or “op-amps”) are high-gain DC coupled amplifiers with two inputs and a single output, and have been used as comparators, audio amplifiers, filters, etc. An operational amplifier is basically a differential amplifier that amplifies the difference between the two inputs. One input has a positive effect on the output signal of the amplifier, and the other input has a negative effect on the output signal. Both inputs act on the output signal simultaneously, and the output signal is the sum of both inputs. Accordingly, if both inputs are equal, then the output signal is ideally zero.
An electronic system incorporating an operational amplifier is frequently required to operate with a large dynamic range. Typically, this requirement means that the electronic system be able to function properly with signal levels ranging from a small signal level to a large signal level. In order for the electronic system to operate well when the signal level is small, the electronic system should introduce little electronic noise. On the other hand, in order to handle large signals, the electronic system should behave in a linear manner so as not to introduce any distortion into its output signal.
Increasingly, the ability to conserve power is being recognized as an important factor in electronic systems. Systems may use operational amplifiers that are designed to support power management by providing two modes of operation, i.e., fully disabled or fully enabled, such as switched capacitor-operational amplifiers. However, as systems become more sophisticated, a more optimized power management capability is desirable, such as through the use of multi-mode operational amplifiers.